package com.rybbaby.tss.core.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * @description MD5加密工具
 *
 * @author 谢进伟
 *
 * @createDate 2016年12月22日 上午15:5:56
 */
public class MD5Util {
	
	private static char hexDigits [] = {'0' , '1' , '2' , '3' , '4' , '5' , '6' , '7' , '8' , '9' , 'a' , 'b' , 'c' , 'd' , 'e' , 'f'};
	
	private static MessageDigest messagedigest = null;
	
	static {
		try {
			messagedigest = MessageDigest.getInstance("MD5");
		} catch (NoSuchAlgorithmException nsaex) {
			System.err.println(MD5Util.class.getName() + "初始化失败，MessageDigest不支持MD5Util。");
			nsaex.printStackTrace();
		}
	}
	
	/**
	 * 将指定文件进行MD5加密
	 * 
	 * @param file
	 * @return
	 * @throws IOException
	 */
	public static String getFileMD5String(File file) throws IOException {
		FileInputStream in = new FileInputStream(file);
		FileChannel ch = in.getChannel();
		MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY , 0 , file.length());
		messagedigest.update(byteBuffer);
		in.close();
		return bufferToHex(messagedigest.digest());
	}
	
	/**
	 * @param str
	 *            将指定字符串进行MD5加密
	 * @return
	 */
	public static String getMD5String(String str) {
		return getMD5String(str.getBytes(StandardCharsets.UTF_8));
	}
	
	/**
	 * @param bytes
	 *            将指定字节数组进行MD5加密
	 * @return
	 */
	public static String getMD5String(byte [] bytes) {
		messagedigest.update(bytes);
		return bufferToHex(messagedigest.digest());
	}
	
	private static String bufferToHex(byte bytes []) {
		return bufferToHex(bytes , 0 , bytes.length);
	}
	
	private static String bufferToHex(byte bytes [] , int m , int n) {
		StringBuilder StringBuilder = new StringBuilder(2 * n);
		int k = m + n;
		for(int l = m ; l < k ; l++) {
			appendHexPair(bytes[l] , StringBuilder);
		}
		return StringBuilder.toString();
	}
	
	private static void appendHexPair(byte bt , StringBuilder StringBuilder) {
		char c0 = hexDigits[(bt & 0xf0) >> 4];
		char c1 = hexDigits[bt & 0xf];
		StringBuilder.append(c0);
		StringBuilder.append(c1);
	}
}